Method of adjusting the frequency of transverse vibrators having a plurality of legs

ABSTRACT

A method of and device for equalizing the frequency and/or symmetry of frequency of transverse vibrators having a plurality of vibrator legs, especially of a two-legged flat fork vibrator serving as frequency normal and/or driving element for timekeeping devices, according to which for purposes of reducing the frequency of a vibrator prefabricated for a higher frequency than the rated frequency, a removal of material is effected at the foot point of the vibrator legs at the outer edge thereof approximately within the region of the lowermost density of the spring lines, the removal of material being effected in conformity with the difference between the starting frequency and the rated frequency.

iJite States Patent [1 1 Meisner et al.

[ Dec.3,1974

[75] Inventors: Alfred Meisner, Nurnberg; Walter Spitzl, l-leroldsberg, both of Germany [73] Assignee: Diehl, Nurnberg, Germany [22] Filed: Dec. 26, 1972 [2]] Appl. No.: 318,570

[30] Foreign Application Priority Data Dec. 24, 197l Germany 2164643 [52] US. Cl 29/596, 29/25.35, 29/169.5, 29/177, 29/593, 58/23 TF, 84/409 [51] Int. Cl. H02k 15/00 [58] Field of Search 29/596, 593, 25.35, 169.5, 29/173, 177; 58/23 TF; 84/409, 407;

3,106,124 l0/l963 Asten ..84/409X l/l966 Rasch 29/l69.5

3,759,l33 9/l973 Budych ct al 84/457 3,760,482 9/l973 Kawamura 29/l69.5

FORElGN PATENTS OR APPLlCATlONS 1,277,362 l0/l96l Francc, 84/409 Primary Examiner-Richard J. Herbst Assistant Examiner-Carl E. Hall Attorney, Agent, or FirmWalter Becker 5 7 ABSTRACT A method of and device for equalizing the frequency and/or symmetry of frequency of transverse vibrators having a plurality of vibrator legs, especially of a twolegged flat fork vibrator serving-as frequency normal and/or driving element for time-keeping devices, according to which for purposes of reducing the frequency of a vibrator prefabricated for a higher frequency than the rated frequency, a removal of material is effected at the foot point of the vibrator legs at the outer edge thereof approximately within the region of the lowermost density of the spring lines, the removal of material being effected in conformity with the difference between the starting frequency and the rated frequency.

6 Claims, 4 Drawing Figures METHOD OF ADJUSTING THE FREQUENCY OF TRANSVERSE VIBRATORS HAVING A PLURALITY OF LEGS The invention relates to a method of and tool for equalizing the frequency and/or frequency symmetry of multileg transverse vibrators, especially of a two-legged flat fork vibrator to be employed as frequency normal and/or driving element for time-keeping devices.

Time-keeping devices have become known according to which a frequency normal and driving element is formed by a mechanical vibrator which consists of a twoor more-legged flat fork, the legs of which are connected at one end, i.e. at the foot end, to each other and to a framework of the device. The other, free ends of the legs carry masses, for instance a permanent magnet which for generating oscillations cooperates with a transistor-controlled coil of an electronic circuit, while means are provided for driving an indicating device. A vibrator or oscillator of this type and driving and output elements associated therewith are illustrated and disclosed for instance in German Offenlegungsschriften 1,773,678 and l,922,640. In order to equalize such vibrators, it is known to add or withdraw mass at the oscillating arms, especially at the free ends thereof, depending on whether the ascertained actual frequency is above or below the rated frequency. A decrease in the mass can be brought about by removing material from the head end for instance by boring or grinding, whereas an increase in the mass can be brought about by soldering material to the mass.

Furthermore, it is known to provide masses for instance in the form of slides which are slidable on the legs of the vibrator so that by displacing said masses or slides in the direction toward the free end, the frequency can be reduced. Finally, above all, for obtaining a fine equalization, it is known to vary the spring coefficient by additional mechanical or magnetic preload.

All of these equalizing methods permit only a small stepwise approach to the rated frequency. Moreover, always two equalizing operations have to be carried out, with larger amounts each time alternately, namely once, the frequency base equalization of the vibrator and secondly, the equalization of the two legs as to symmetry or frequency identity. Such equalization therefore is rather time-consuming and expensive.

It is, therefore, an object of the present invention to provide an equalizing method which will be suitable for mass production and which can be automated to a major extent.

It is another object of this invention to provide a method as set forth in the preceding paragraph, which will assure that after ascertaining the starting frequency of the vibrator and of the frequency symmetry of its two legs, during the subsequent equalization operation both corrections can be effected together.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 is a side view of a flat fork vibrator input and output device, which vibrator has been equalized in conformity with the method of the present invention.

FIG. 3 is a front view of an equalizing tool formed by a two-punch punching tool.

. FIG. 4 is a section taken along the line IVIV of FIG. 3 and shows a section through the tool and a view of the inserted vibrator in starting position.

According to the present invention, for reducing the frequency of a vibrator which during its prefabrication has been dimensional for a higher frequency than the rated frequency, a reduction of the material corresponding to the difference between the starting frequency and the rated frequency is carried out at the foot point of the vibrator leg and, more specifically, at the outer edge thereof approximately within the region of the lowest density of the spring tension lines. This is effected by material removal progressing from a lateral notching of the vibrator legs in the direction toward the ends of the legs. In this connection, the creation of the symmetry (right-hand fork to left-hand fork) of the leg frequency is obtainable by lateral preadjustment of the depth of removal, whereas the common reduction in frequency of both legs is obtainable by a longitudinal removal on the vibrator by displacement of the vibrator relative to the material removing tool acting at both sides on the edges of the vibrator. The difference in frequency between the two vibrator legs serves as measurement for the lateral adjustment while the difference in frequency of the total vibrator from the rated frequency serves as measurement for the decrease in the spring tension due to the removal of material. The removal of material may be effected by progressive punching off of the leg edges from a base constriction in the fork foot in the direction toward the leg ends.

On the basis of the first given actual frequency and a frequency non-symmetry measurement, the above mentioned equalization method makes it possible to ascertain the reduction in the spring tension to be effected on both sides and also permits of precisely carrying out of said last mentioned decrease in the spring tension by a simple removal of material in a region poor in the spring tension lines. Inasmuch as the tension occurring in the material during the punching off operation extends likewise only to the marginal zone which is low in spring tension lines, an equalization by postheating or the like will not be necessary.

Referring now to the drawings in detail, the arrangement shown in FIG. 1 illustrates a frame 7 for the timekeeping device. By means of screws 6, a flat fork vibrator l is connected to the frame 7. As illustrated in FIG. 2, the vibrator comprises a connecting flap 4 which by a notched lateral constriction 5 is separated from a fork foot 3 where the legs 8 and 9 of the vibrator 1 end. The head end of leg 8 has connected thereto a mass in the form of a U-shaped frame 10 which is standing on edge or upright and by means of a plate 11 is connected to said leg 8. The leg 9 is provided with a cylindrical permanent magnet 14 which extends upwardly and is arranged centrally in the frame 10 while being connected to a supporting plate 13. This permanent magnet 14 cooperates with a coil 15 which forms the part of a transistor-controlled electronic circuit for inciting the vibration or maintaining the same. The same supporting plate 13 is furthermore provided with two downwardly extending arms l6, 17 which comprise stepping or feeding magnets l8, 19 that extend toward each other and cooperate with a stepping wheel 20. The design and operation of the vibrator 1 as well as of the above mentioned structural elements is set forth in detail in the German Offenl egungsschriften 1,733,678 and 1,922,640. I I

The vibrator l which consists of a high grade material as is used for instance for balance springs, is during its prefabrication, i.e. during the punching out of the vibrator 1 itself and when dimensioning the masses 10, ll; 13, 14, 16-19, given a starting frequency of for instance 105 cyclesper second, which means a frequency which is higher than the rated frequency of for instance 100 cycles per second. Inasmuch as the material coefficients and dimensionscannot be precisely repeated, which means that the values are not always the same, the starting actual frequency of the vibrator l varies for instance by i two cycles per second. Similarly, the frequencies of the two legs may-differ from each other which means they are not in resonance. Both values, i.e'. the starting frequency as well as the frequency nonsymmetry can be ascertained in a control circuit corresponding to the time-keeping device. These values and their deviations represent the measurement for the corrective steps to be taken with the subsequent equalization operation.

ln FIG. 2, the thin lines 12 illustrate the spring tension lines in the vibrator 1. As will be 'seen from FIG. 2, these lines crowd each other above all at the end of a slot 2 within the region of the fork foot 3, said slot2 separating the two legs 8, -9 from each other. Toward the edge, the density of said lines becomes less and less, which means a change in the dimensions of the legs 8, 9 starting from the slot 2, within the region of the fork foot 3, would influence the spring properties to a considerably greater extent than at the edge, for instance within the range of the notches 5.

in order to be able'to lower the actual frequency in small steps precisely to the rated frequency, spring material is removed at the edge and, more specifically; starting from the notches 5 in the direction toward the head of the legs. While by removal of material'there is obtained a reduction in the mass on one hand, it will be evident that on theother hand also the intensity of the spring is weakened. As long as the removal of material is effected within the region of the fork foot 3, this removal of material will make itself felt only by the reduction in the spring intensity. However, when the removal of material progresses toward the front in the direction toward the head, also a progressively effective reduction in the mass occurs. By the reduction of material at the edge, therefore, the equalization can be effected very precisely. Depending on whether the leg 8 or 9 has a higher starting frequency, more material will be removed at the edge of leg 8 or at the edge of leg 9. These two areas of removal of material are designated with the reference numerals 21 and 22. The starting form of the vibrator l or its legs 8 9 is indicated by dotdash marginal lines.

The removal of material may be effected in any desired form, for instance by a dosed, preferably simultaneous, grinding into or grinding off or by sawing or milling the rim, preferably starting from the notches 5. A particularly simple and fast material removal, which is simultaneously effected on both sides, is obtained by punching off or out operations. The tool which is required for this purpose is illustrated diagrammatically in FIGS. 3. and 4. This tool consists of two punches 23, 24 which are arranged at a fixed or variable distance with regard to each other and are vertically displaceable in a guiding plate 25 and a cutting plate 26 while onthe inner side being provided with cutting surfaces or cutting edges 27, 28. ln the space between said punches 23, 24 the vibrator l is by means of a carriage indicated by arrows a and b insertable in longitudinal direction and adjustable laterally toa limited extent. A preadjustment in the direction of the arrow a serves for establishing frequency symmetry which means that it serves for the determination of the resonance of the two legs 8, 9 with subsequent punching operation. The more or less frequently and widely effected stepwise displacement of the vibrator l in the direction of the arrow b with each respective punching operation serves the uniform frequency equalization of the vibrator 1 up to the rated frequency. The vibratorl is preferably located in a receiving depression of the carriage (not iliustrated). Inasmuch as the punching sections are sufficiently great in order to permit a proper controlling and elimination, no danger exists during the punching operation that mass particles get stuck in the head for instance on the permanent magnet 14 and on one hand may falsify'the equalization result and on the other hand may later on interfere with the proper operation.

it is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings but also comprises any modifications within the .scope of the appended claims.

We claim:

l. A method of adjusting and balancing the frequency and frequency symmetry, respectively, of a transverse flat fork vibrator which comprises a normally flatelement in substantially one plane having a connecting flap at one end, a foot portion integral with said flap and a pair of legs extending from said foot portion and terminating in free ends and which vibrate perpendicularlyto the plane of said vibrator, said legs being spaced by a slot extending from said foot portion to said free ends of said legs, said method comprising selectively removing material from the outer edges of said legs at their junction with said foot portion and opposite the end of said slot adjacent said foot portion, to reduce the frequency of vibration of said legs to a predetermined frequency and to equalize the vibration frequencies of the pair of legs.

2. A method according to claim 1, in which the removal of material is effected by material removing tools, progressively from the foot portion of the vibrator legs on opposite sides of the vibrator in the direction toward the leg ends.

3. A method according to claim 2, which includes the step of providing the transverse vibrator on opposite sides at the foot portion with a curved notched portion, and effecting the removal of material progressively from said notched portion of the foot portion in the direction toward the leg ends.

4. A method according to claim 2, which includes the steps of effecting the symmetry of the frequency of the vibrator legs by a lateral pre-adjustment of the vibrator relative to the material removing tools, and effecting the uniform reduction in frequency by a longitudinal displacement of the vibrator relataive to the material removing tools.

5. A method according to claim 4, which includes the steps of: ascertaining the starting frequency of the vibrator and the vibrator legs, subsequently in conformity with the deviation of the actual starting frequency moval of material is effected by progressively punching material from the edges of the vibrator legs in the direction toward the leg ends, the basic frequency deviation from the rated frequency being taken as an indication for the number and length of the necessary progressive punching steps. 

1. A method of adjusting and balancing the frequency and frequency symmetry, respectively, of a transverse flat fork vibrator which comprises a normally flat element in substantially one plane having a connecting flap at one end, a foot portion integral with said flap and a pair of legs extending from said foot portion and terminating in free ends and which vibrate perpendicularly to the plane of said vibrator, said legs being spaced by a slot extending from said foot portion to said free ends of said legs, said method comprising selectively removing material from the outer edges of said legs at their junction with said foot portion and opposite the end of said slot adjacent said foot portion, to reduce the frequency of vibration of said legs to a predetermined frequency and to equalize the vibration frequencies of the pair of legs.
 2. A method according to claim 1, in which the removal of material is effected by material removing tools, progressively from the foot portion of the vibrator legs on opposite sides of the vibrator in the direction toward the leg ends.
 3. A method according to claim 2, which includes the step of providing the transverse vibrator on opposite sides at the foot portion with a curved notched portion, and effecting the removal of material progressively from said notched portion of the foot portion in the direction toward the leg ends.
 4. A method according to claim 2, which includes the steps of effecting the symmetry of the frequency of the vibrator legs by a lateral pre-adjustment of the vibrator relative to the material removing tools, and effecting the uniform reduction in frequency by a longitudinal displacement of the vibrator relataive to the material removing tools.
 5. A method according to claim 4, which includes the steps of: ascertaining the starting frequency of the vibrator and the vibrator legs, subsequently in conformity with the deviation of the actual starting frequency from the rated frequency determining the necessary longitudinal displacement of the vibrator relative to the material removing tool, and laterally presetting the vibrator legs relative to the respective material removing tool in conformity with the starting natural frequency of each of said vibrator legs.
 6. A method according to claim 1, in which the removal of material is effected by progressively punching material from the edges of the vibrator legs in the direction toward the leg ends, the basic frequency deviation from the rated frequency being taken as an indication for the number and length of the necessary progressive punching steps. 